Stirred‐tank mechanical power requirement and gas holdup in aerated aqueous phases

Abstract

Gas holdup and the ratio of the turbulent regime mechanical power consumed in aerated compared to that in nonaerated aqueous phases were measured in two laboratory sized tanks. Standard six‐blade turbine (D/T = 1/3), six‐blade paddle (D/T = 1/3), and four‐blade paddle (D/T = 2/3) impellers were used over a wide range of impeller rotational speed and gas sparging rate. For all systems, the power ratio results were found to fit a semitheoretical correlation (derived from dimensional analysis) involving the impeller Weber number, the aeration number, and the ratio of dispersion and liquid densities. Empirical correlations for gas holdup in water, aqueous solutions of nonelectrolytes, and an aqueous electrolyte solution are given. The overall results lead to the conclusion that power ratio and gas holdup correlations are highly specific to a particular impeller type and are also dependent on the tank size and the liquid phase physicochemical properties.

Vapour generation from the impellers in boiling stirred tank reactors

“…2b, for reference, the present data in the boiling system are compared with the predictions of the correlation for P/P 0 for a six-blade disk turbine in gas-sparging systems. The correlation proposed by Hassan and Robinson (1977) may be written as follows:…”

Gas Holdup and Bubble Diameters in Pressurized Gas-Liquid Stirred Vessels

“…A good review of these correlations is given by Hassan and Robinson (1977). The literature does not contain any measurements of power consumption in pressurized reactors due, no doubt, to the experimental difficulties involved.…”

Prediction of Power Consumption in a Mechanically Agitated Gassed Reactor in Viscous Batches

“…where Po i are the power numbers of individual impellers. One of the first widely used correlations of the impeller power draw under aeration for a Rushton turbine was proposed by Michel and Miller : …”

“…where T means the vessel diameter. One of the first widely used dimensionally consistent correlations was proposed in , based on the relation introduced by , , who tried to correlate the relative power draw under aeration, P g / P u . Using experimental results for various liquids , they derived the following correlation extended by the Weber number We : …”